To jerk off; To get with someone; You say "Shema!" when your excited; You also say "Shemaaaa" when you have to do something but don't want to; Pretty much you can say it whenever you want, use it as a noun, adjective or verb

Originated by Sean Donnelly and Kurt Spinner after the liking of farm-boy Gary and Chrisssss`

"Did you shema last nite?"
"Did you shema around with her?"
"Shema! I just won the lottery!"
"Go take out the garbage....Shemaaaaaaa..."
"Well, Shema, let's go then."